The invention relates to an electronic controller for a motor vehicle automatic transmission and a method for calibrating a position detection sensor in an electronic controller for a motor vehicle automatic transmission.
Automatic transmissions for passenger vehicles are usually controlled electronically. The controllers for such transmissions have previously been provided as what are referred to as stand-alone units in a control box protecting against ambient influences or have been directly installed in the passenger compartment of the vehicle. Recently, there has been a change over to integrating the electronic control system and the associated sensor systems directly into the automatic transmission for reasons of costs and quality. Fundamental system requirements for the operation of the electronics in the transmission include having operational capability over a wide temperature range, for example, xe2x88x9240xc2x0 C. to 140xc2x0 C., being leak proof with respect to transmission ATF oil, and having sufficient immunity to vibration, for example, 30 g. An optimized configuration with respect to temperature is achieved by bonding the electronic circuit on the ceramic substrate onto a metal base plate, for example, made of aluminum, using a thermally conductive adhesive.
In addition to rotational speed sensors, pressure sensors, and temperature sensors, customary transmission controllers for automatic transmissions have a position detection sensor that is used to sense which driving mode of the automatic transmission is set. The sensing is carried out, for example, by setting what is referred to as the selector mode switch into one of the positions xe2x80x9cPxe2x80x9d (Park), xe2x80x9cRxe2x80x9d (Reverse), xe2x80x9cNxe2x80x9d (Neutral), or xe2x80x9cDxe2x80x9d (Drive). The selector mode switchxe2x80x94also referred to below as selector leverxe2x80x94is mechanically connected to the automatic transmission in that it activates a selector slide that can move in a linear or rotary fashion. The selector slide is integrated into the hydraulic part of the transmission controller. The electronic controller is informed of the driving position that has been set by the sensing of the selector slide position using the position detection sensor.
For position detection, the prior art includes providing an independent sensor that is packed in an oil-tight fashion in a housing to protect against the ambient medium, namely transmission oil. The electrical connection of the sensor through corresponding lines to the controller must also be configured in an oil-tight fashion.
Various measuring principles are conceivable for the configuration of the sensors. German Patent DE 196 03 197 C1, corresponding to U.S. Pat. No. 5,969,519 to Steiling et al., discloses the use of magnetic field sensors that are based on the Hall effect. In such configurations, measurement quality is influenced to a considerable extent by the air gap between the magnet and sensor element. For this reason, a triggering element (PES slide) that is embodied as a slide and in which an encoded magnetic plate or a signal-transmitting magnet is integrated is guided with precise tolerances in guide grooves of the sensor housing. The transmission-internal selector slide engages in the PES slide and is rigidly connected to the selector lever in the interior of the vehicle through a linkage or a bowden cable. If the selector lever is moved from one position into another, the movable PES slide is also adjusted by the selector slide in the transmission so that the electronic transmission system can read in the new selector lever position.
Position detection sensors that are based on the Hall effect are embodied in an exclusively digital fashion, as are position detection sensors that are based electromechanically on the switch or slider principle. The absolute precision of the system results from a chain of tolerances of the electronic and mechanical components involved. A static correction after installation in the vehicle is no longer possible.
The post-published European laid-open application European Patent Application EP 1 046 839 A2 discloses an electronic controller for a motor vehicle automatic transmission with a position detection sensor. The sensor supplies an analog output signal as a function of the position of a selector slide and can be calibrated, even during operation, by an algorithm that is stored in the electronic control system.
The publication German Published, Non-Prosecuted Patent Application DE 43 40 917 A1 also discloses an electronic controller for a motor vehicle automatic transmission with a position detection sensor. Here, too, the sensor supplies an analog output signal as a function of the position of a selector slide. A calibration program that is stored in the electronic control can calibrate the system position detection sensor.
It is accordingly an object of the invention to provide a electronic controller for a motor vehicle automatic transmission and method for calibrating a position detection sensor in an electronic controller for a motor vehicle automatic transmission that overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and that integrates a position detection sensor into an electronic controller in a simple and cost-effective way and with sufficient precision, and that permits the sensor to be calibrated after installation in the vehicle, the calibration statusxe2x80x94calibrated or uncalibratedxe2x80x94of the position detection sensor being able to be established quickly and with little outlay.
With the foregoing and other objects in view, there is provided, in accordance with the invention, an electronic controller for a motor vehicle automatic transmission, including a housing, a selector slide moveable into a plurality of positions, a position detection sensor for sensing a position of the selector slide, and an electronic control system for controlling the automatic transmission. The position detection sensor is disposed in the housing, supplies an analog output signal dependent upon a position of the selector slide, and has a calibration status. The electronic control system is disposed in the housing, is electrically connected to the position detection sensor, and is programmed to calibrate the position detection sensor and identify the calibration status.
In addition to digital sensors (Hall sensors) analog sensor principles, for example, based upon a permanent magnetic linear contactless displacement sensor (xe2x80x9cPLCDxe2x80x9d) are in the prior art for position detection sensors. A PLCD is based on a coil configuration, which contains an integrated electronic evaluation circuit, for example, as an ASIC module, and generates an analog output signal, preferably a voltage signal, based upon the position of signal-transmitting magnets relative to the sensor.
In position detection sensors, the precision with which the selector modes (P, R, N, and D) can be sensed is a decisive quality feature. In contrast to digital position detection sensors, with analog position detection sensors it is possible to compensate the sensor statically to largely eliminate fabrication and installation tolerances of the position detection sensor in the transmission and in the vehicle, and, thus, increase the precision in the system.
In accordance with another feature of the invention, there is provided a signal-transmitting magnet disposed directly on the selector slide.
In accordance with a further feature of the invention, the position detection sensor has an output, and the output is a redundant differential interface supplying the analog output signal and a complementary signal.
In accordance with an added feature of the invention, the position detection sensor is a permanent magnetic linear contactless displacement sensor.
In accordance with an additional feature of the invention, the selector slide is adjacent the housing.
In accordance with yet another feature of the invention, the housing is substantially oil tight.
In accordance with yet a further feature of the invention, the electronic control system is programmed to represent the calibration status with a status identifier.
With the objects of the invention in view, there is also provided a method for calibrating a position detection sensor in an electronic controller for a motor vehicle automatic transmission, including the steps of selecting one of a plurality of selector modes of a selector slide, determining which one of the selector modes the selector slide is in, supplying an analog output signal from the position detection sensor as a function of a position of the selector slide, determining a signal level of the analog output signal and storing the signal level in a non-volatile memory of an electronic control system, repeating the above steps until a predetermined number of signal levels is stored for at least two of the selector modes, determining signal level bands for respective ones of the at least two selector modes based upon the stored signal levels and storing the signal level bands in the non-volatile memory, calculating signal level bands for other ones of the selector modes based upon the stored signal levels and also storing the calculated signal level bands in the non-volatile memory, and resetting a status identifier in the electronic control system if signal level bands are stored in the non-volatile memory for all of the selector modes.
In accordance with yet an added mode of the invention, in the electronic control system, a calibration status of the position detection sensor is represented with a status identifier.
With the objects of the invention in view, there is also provided a method for calibrating a position detection sensor in an electronic controller for a motor vehicle automatic transmission including the steps of providing a selector slide having a plurality of selector modes and positions, supplying an analog output signal from the position detection sensor as a function of a position of the selector slide, determining a predefined number of signal levels of the analog output signal for at least two of the selector modes and storing the signal levels in a non-volatile memory of an electronic control system, determining signal level bands for respective ones of the at least two selector modes based upon the stored signal levels and storing the signal level bands in the non-volatile memory, and calculating signal level bands for other ones of the selector modes based upon the stored signal levels and also storing the calculated signal level bands in the nonvolatile memory.
In accordance with a concomitant feature of the invention, a status identifier is reset in the electronic control system if signal level bands are stored in the non-volatile memory for all of the selector modes.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a electronic controller for a motor vehicle automatic transmission and method for calibrating a position detection sensor in an electronic controller for a motor vehicle automatic transmission, it is, nevertheless, not intended to be limited to the details shown because various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.